[j-nsp] Internet routes in MPLS network, global table or own VRF?

Pavel Lunin plunin at senetsy.ru
Thu Jan 26 16:33:38 EST 2012

> > Because FRR uses a path from a different entry (PLP) to probably a
> different

Ups, I meant PLR, of course.

>  > exit (say, next-next-hop). When normal LSP (either SPF or CSPF
> calculated)
> > is a path from head-end to tail-end. Whether this happens often or rare,
> the
> > need to care how your detours are calculated is itself a big enough
> > headache.
> That's not how FRR works at least for RSVP.  It pretty much just
> re-runs cspf with something removed.  So it's the same route your IGP
> would choose if said "thing" went dark.  I don't have many obscure
> paths where I wouldn't want traffic to go so I can't really comment on
> your earlier idea.  That being said I've never seen FRR choose a path
> worse than the path the IGP would choose.  It's just preselects that
> path and pre-signals it.  I'm sure there are failure scenarios though.
Seems like you confuse FRR (aka local repair) with secondary LSP path. FRR
path setup is initiated by P routers, when the primary and secondary LSP
paths are initiated by head-end PE. FRR detour only holds until IGP
recalculates a new path (doesn't much matter with or without TE), which can
(and very probably will) not even include the P router, acted as a point of
local repair after failure.


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